Post by thread:using page 0 registers on page 1

Edward Cheung (spam_OUTebc714TakeThisOuTrs710.gsfc.nasa.gov) wrote: >[Quoting me:] >>AND the assembler will >>give you warning whenever you accidently treat a page-0 register as >>though it were on page 1. > >This does not verify that you have set the page bit right? It only >makes sure you don't use the wrong variable name. Thus if you wanted >to say : >MOVFW PORTA >but instead typed >MOVFW TRISA >The mechanism you mentioned (XORing the variable name) will catch >this type of error only. Is my assumption correct. Edward: Hope you don't mind my copying this reply to the list... It may be useful to others. Yes, your assumption is correct; the page bits still need to be set properly. Currently, I'm using a VERY complicated (well, complicated to create, anyway... they're totally invisible when used) set of instruction-redefining MPASM macros to take care of the page-selection automatically. The example you give isn't the best (although the "xor" will catch that error); a much-more common error occurs when you're using a part whose general-purpose registers aren't shadowed in all register banks (e.g., 16C57, 16C74, etc.), and you simply forget which bank a register is in. For instance: REG1 EQU [any page-0 register] REG2 EQU [any page-1 location] .... BSF STATUS,RP0 ;Switch to page 1. MOVF REG2^080H,W ;Copy the contents of REG2 to REG1. MOVWF REG1^080H ; BCF STATUS,RP0 ;Switch back to page 0. In this case, MPASM will generate a warning on the REG1 access. If we'd used "&07FH" instead of "^080H", no warning would have been produced. -Andy -- Andrew Warren - .....fastfwdKILLspam@spam@ix.netcom.com Fast Forward Engineering, Vista, California

>Hope you don't mind my copying this reply to the list... It may be Not at all. Thanks for your clarification on the page switch idea. I had originally skimmed over your post to the list, thought it was a great idea, and then filed it away for later study. When I did study it, I was a little confused and asked you the question. That is why I sent you two notes. I still think your idea is brilliant. +---------------------------------------------------------------------------+ | Edward Cheung, Ph.D. | The opinions expressed herein | | NASA Goddard Space Flight Center | do not necessarily reflect | | Code 714.1, Bldg T11B | those of my employers' | | Greenbelt, MD 20771 | | | 301-286-1269(office) 286-1717(fax) | My next book: | | Internet: ebc714KILLspamrs710.gsfc.nasa.gov | Statistics, Demos and Other Lies | +---------------------------------------------------------------------------+